<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>ID选择器</title>
        <style>
            body{color:red;}
            #one{color:green;}
            #two{color:blue;}
        </style>
    </head>
    <body>
        body的内容
        <div id="one">
            id是one的div标签
        </div>
        <span id="two">id是two的span标签</span>
    </body>
</html>